A. Field of Invention
This invention pertains to a railroad wheel sensor and more particularly to a temperature sensor with a plurality of infrared detectors arranged in an array for detecting hot wheel flanges and/or hot wheel bearings.
B. Description of the prior art
A major source of problems in the field of railroad transportation and especially freight railroad trains have been overheated bearings. Am overheated bearing on a single car truck may collapse, causing the car to overturn and the train to derail. Such derailments are extremely dangerous, and can cause immense economic expense. In order to prevent such derailments, infrared hot bearing detecting apparatus are presently in service on railroads in virtually every major country in the world. The original system for these detectors was installed in the United States in 1956. Typically, such systems use an infrared scanner disposed on the railroad bed adjacent to the track and oriented at an angle upwardly so that it scans successively the bearing covers and the bottom of the railroad car. The readings obtained from the car bottom is used as an indicia of the ambient temperature. Over the years various changes have been made in the design of railroad cars and the detectors must have the ability to scan and accurately measure the temperature of the bearings on a large number of car configurations. Existing detectors have problems accomplishing this task successfully. For example, the latest articulated freight cars do not present a uniform bottom to the scanner which can be used as an accurate ambient temperature reference. Another problem with existing detectors has been that the bottom of empty freight cars may get heated up by the sun giving a false indication of the ambient temperature.
Another problem for railroads results from overheated wheels due to defective brake mechanisms. These mechanisms heat the wheels of a car to dangerous levels, causing the wheel flanges to lose their tensile strength. Of course the dangerous temperature limit for a hot wheel flange is much higher that the dangerous temperature limit for a hot bearing and therefore a temperature for a wheel flange may be perfectly acceptable but may be too high for a bearing. Until now this and other various physical constraints dictated the use of separate hot wheel flange and hot bearing detectors. In fact many hot bearing detectors included means for occluding any hot wheel flange readings to insure that a normal wheel flange reading does not result in a false hot bearing reading. Of course a false hot bearing reading (or for that matter, a false hot wheel flange reading), while not as dangerous, is also very expensive if it result in the stopping of a train. Moreover, existing detectors used only a single temperature sensor and required complicated circuitry to properly recognize a hot wheel flange or wheel bearing.
U.S. Pat. No. 2,818,508 to Johanson et al. discloses a hot bearing detector with a scanner oriented transversely to the train movement, and a wheel sensor which disables the scanner to insure that hot wheel readings are excluded.
U.S. Pat. No. 3,545,005 to Gallagher discloses a hot bearing detector with a mechanical shutter operated by a wheel.
U.S. Pat. No. 3,253,140 to Sibley et al. discloses a system with an angled detector for recording the temperature of a wheel hub, wheel web and wheel flange.